FRANKFURT (Reuters) - Deutsche Bank may have been used by some of its Russian clients as a hub for money laundering to a greater extent than previously assumed, a source familiar with the matter said on Tuesday.

The Deutsche Bank headquarters are seen in Frankfurt, Germany October 28, 2015. REUTERS/Kai Pfaffenbach/Files

The lender has found a total of $10 billion of suspicious trades, including $6 billion in so-called “mirror trades” that it identified earlier this year, the source said, adding that it had shared this information with watchdogs in September.

The “mirror trades” may have allowed Russian customers to move money from one country to another without alerting the authorities, potentially allowing them to breach the sanctions against Russia after its 2014 annexation of Crimea.

Deutsche Bank, which declined to comment on the size of the trades, said it is investigating certain equity trades in Moscow and London, adding the total volume of the transactions under review is “significant”.

Deutsche Bank has been spent most of the year trying to put a series of legal and regulatory problems entailing billions of dollars in fines and settlements behind it and focus a new strategy. [nL8N12T36R]

New Chief Executive John Cryan said in late October Deutsche Bank was “vulnerable” in respect to possible large penalties for the Russian trades, adding provisions for them may not suffice.

A source familiar with the matter said Deutsche has for now put less than 1 billion euros aside for the issue. “But the case has the potential of becoming as big as Libor,” the source said.

Earlier this year U.S. and British regulators fined Deutsche Bank $2.5 billion for its involvement in a global interest rate rigging scheme.

The Russia trades are now among Deutsche’s top remaining legal headaches alongside the misselling of U.S. mortgages in the run-up to the financial crisis and the investigation into the Chinese “princeling” issue of hiring children of government officials as a way to attract business.

While Deutsche Bank is sharing its Russia findings with European watchdogs such as the ECB, Germany’s Bafin and Britain’s FCA, the U.S. Justice Department and New York State’s Department of Financial Services (DFS) are involved because some U.S. citizens were allegedly part of the transactions, and because many of the trades were done in dollars.

The investigations focus on so-called “mirror trades”, which could allow the movement of funds from one country to another without passing through normal procedures for cross-border money transfers.

The bank, which launched an internal probe into Russian securities trades in June, is also being examined to see if it had compliance programs ready for Russian sanctions and provided accurate information to regulators.

Russia’s central bank recently handed Deutsche a small fine of $5,000 for procedural shortcomings, but said that the bank was a victim of an illegal scheme and had hade taken measures to improve its systems, the source familiar with the matter said.

The Russian central bank was not immediately available for comment.

Deutsche Bank has already decided to close its investment banking activities in the country, resulting in a reduction of its headcount by around 200 jobs in Russia from 1,300 it had in the middle of this year.